STAMFORD, Conn. — It was unusual when Antonio Muralles, 52, did not show up for work on Thursday morning.

He had worked at the warehouse in Connecticut since he arrived in the country two decades ago from Guatemala, making things used by workers who make other things. The company made coveralls and rigger bags, gloves and protective eyewear.

Mr. Muralles became expert on the machine used to make chain saws. He would go on to become the warehouse manager, but would still work the chain-saw machine. As he built a life and settled into his new home, the people at the company, Green Mountain Products, became a second family.

“He was like a son to the owner and my best friend, and like an older brother to the girls,” said Matthew Deedon, the plant manager.

The police arrived later in the day with news that shocked his co-workers.

Shortly after 8 p.m. on Wednesday, Mr. Muralles was leaving a McDonald’s just around the corner from his apartment in Stamford, a cup of coffee in hand, as he often did.

As he was leaving, a group of young people were out looking for trouble, the police said. They were taunting strangers, poking people with a stick and trying to provoke a fight, Lt. Deidrich Hohn, a detective with the Stamford Police Department, said in an interview on Tuesday.

When Mr. Muralles crossed their path, he was stabbed, beaten and left for dead. There were witnesses but no one intervened. Only one person called 911.

The Stamford police chief, Jon Fontneau, said in an interview that Mr. Muralles walked out of the McDonald’s and bumped into the group. Chief Fontneau said someone poked Mr. Muralles with a stick; he backed into a defensive posture and accidentally spilled some coffee on a 15-year-old, Marquest Hall, who was there with a 22-year-old friend. Mr. Hall pulled out a knife and stabbed him repeatedly, Chief Fontneau said.

“The 15-year-old stabbed him in the chest,” Lieutenant Hohn said. “Then the 22-year-old jumped on him and started beating him. And then the 15-year-old stabbed him again and again.”

The McDonald’s, at Bedford and Broad Streets, sits in the heart of downtown Stamford’s business and shopping district, near the Landmark Square office complex, Stamford Town Center shopping mall and Ferguson Public Library.

“At least 10 people drove by and walked by this thing when it was going on, and we only got one call,” Lieutenant Hohn said. “People just don’t pay attention or are afraid to get involved.”

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A memorial to 52-year-old Stamford resident Antonio Muralles, who was stabbed to death last week outside of McDonald's in Stamford, Conn.CreditChristopher Gregory for The New York Times

It happened that moments after the attack, a Fire Department crew was driving by on an unrelated matter when they saw Mr. Muralles collapse on the street.

They rushed to help, thinking he had a medical problem. When they opened his shirt, it was clear that he had been stabbed.

Mr. Muralles died four hours later on Thursday at Stamford Hospital.

Lieutenant Hohn said that because only one person called to report the episode, finding the attackers proved difficult. The police sifted through hours of video footage from 10 nearby surveillance cameras.

A woman, shocked by the crime, the city’s first homicide this year, eventually came forward to say she had witnessed the attack. There was also a tip to a narcotics officer. Within 72 hours, the police identified the prime suspects.

On Sunday, James McLamb, 22, of New Haven, was arrested on an unrelated charge. He was quickly identified as being wanted in the attack and on Monday was charged with murder.

Mr. Hall was arrested on Monday. His case was transferred from juvenile to the adult criminal court on Tuesday in Superior Court in Stamford, and he was charged with murder.

Mark Sherman, a lawyer for Mr. Hall, said his client had a history of mental health problems but declined to speak in detail about the case.

The police said on Tuesday that they expected to make a third arrest, but noted that that person would not be charged with murder.

Lieutenant Hohn said that there had been an uptick in violent crime in downtown Stamford, but that he could not recall a crime as vicious as this.

When the police announced the arrests, they made a point of inviting the Muralles family to the news conference.

Mr. Muralles lived with his niece, Rosa Olivares, 39, her husband and their three children.

“On the weekends the family would get together, and he would bring the happiness because he played the guitar,” Ms. Olivares said. “He would sing romantic songs, rancheras and classic songs.” She said her uncle had wanted to visit his 93-year-old father in Guatemala.

“In Guatemala, he was a farmer,” she said. “He farmed corn and beans in fields to sell and he lived off of that. He decided to come to the United States for a better life.”

Kristin Hussey reported from Stamford, and Marc Santora from New York. Sandra E. Garcia contributed reporting from New York.

A version of this article appears in print on , on Page A21 of the New York edition with the headline: 2 Charged With Murder in Stabbing of Man as He Left Stamford McDonald’s. Order Reprints | Today’s Paper | Subscribe